CVE-2026-21873 HIGH

CVE-2026-21873: Zero-click XSS in all NiceGUI apps which uses `ui.sub_pages`

Vendor Zauberzeug
Product nicegui
Weakness CWE-79 · XSS
Published January 8, 2026
Last update January 8, 2026
View on NVD All CVEs

CVSS base score

7.2/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality Low
Integrity Low

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

What the vulnerability does

01Description

NiceGUI is a Python-based UI framework. From versions 2.22.0 to 3.4.1, an unsafe implementation in the pushstate event listener used by ui.sub_pages allows an attacker to manipulate the fragment identifier of the URL, which they can do despite being cross-site, using an iframe. This issue has been patched in version 3.5.0.

Key dates

02Disclosure timeline

January 8, 2026 CVE published
January 8, 2026 Record updated